Mobile access networks provide a facility for mobile nodes to communicate data so that a variety of services can be provided to mobile users. As a mobile node roams through a geographical area, the mobile node may have an opportunity to become attached and to communicate data via different mobile access networks. For example, if a mobile node roams away from a coverage area of the mobile node's home mobile access network, the mobile node may have an option of becoming attached to more than one visited access network. Whilst, conventionally mobile nodes are arranged to communicate data via a single wireless access interface standard such as UMTS/GPRS or WiFi, mobile nodes may also be arranged to communicate via a plurality of different interface standards or indeed fixed wire access networks. Therefore a mobile node may have an option of attaching to different mobile access networks, which operate in accordance with the same wireless access interface standard or different interface standards.
An operator of a mobile access network to which the mobile node is affiliated may wish to control the mobile access network to which the mobile node becomes attached. The operator may be motivated to control which access network is used for economic and/or network performance reasons. For example, in WO-A-03047296, a mobility manager of an operator network is provided with change of affiliation requests coming from a mobile node which are examined by the mobility manager. The mobility manager then makes a mobility decision regarding whether or not to change the affiliation of the mobile node to another access network. If so, the mobility manager controls the change of affiliation in accordance with that mobility decision.